grd@cm-next-9.Stanford.EDU (glen diener) (11/04/90)
Here's what I came up with for Seagate's Wren 7 SCSI
(1200 meg unformatted). This disk contains all
the home directories of all users of our 13-NeXT machine
site. I wanted one big partition for this task, avoiding
the labor of shuffling users from partition to partition
to balance the usage, and can easily back up the whole
thing to a single exabyte cartridge.
# Seagate Wren 7 5.25 " 1200 meg
IMPRIMIS94601-15|Wren-7|Wren 7 with 512 byte sectors:\
:ty=fixed_rw_scsi:nc#1931:nt#15:ns#35:ss#1024:rm#3600:\
:fp#160:bp#0:ng#0:gs#0:ga#0:ao#0:\
:os=sdmach:z0#32:z1#96:\
:pa#0:sa#1015600:ba#8192:fa#1024:ca#32:da#4096:ra#10:oa=time:\
:ia:ta=4.3BSD:
The usable capacity looks like this:
Filesystem kbytes used avail capacity Mounted on
/dev/sd1a 998991 9 899082 0% /mnt
Running disk's ``read'' test...
# sectors per transfer? 16
number of transfers? 1000
sector increment? 16
16384000 bytes in 18079 ms = 906696 bytes/s
This whole disktab thing seems like a black art. I have yet to find
any documentation/explanation about front and back porch size,
dealing with ``cylinder-oriented sparing'', the infamous
``tuning the file system rotational latency parameter'', etc. etc.
The disktab entry was really hacked together with little background
knowledge. Surprisingly enough, however, it works! Nevertheless, if
anyone out there has a handle on this stuff, I'll bet many of
us would benefit from a little enlightenment...
-glen diener
grd@ccrma.stanford.edu